question is what if any difference will there be with longer crank arms. my SS has 165...i ride 172.5 on road bike so will longer crank arms play role is speed, climbing, spinning All things being equal ....at a given power out put, tempo will longer cranks influence.
the 165 just feel to small.

Conventional wisdom holds that more length = more climbing power, like swinging a sledgehammer vs a ball-peen. It also means less ground clearance when cornering, which is one reason why fixed gear bikes have shorter crankarms.

According to Jim Martin's study, however, "in a crank range of 145 to 170 mm, the difference in power was a miniscule 1.6%."

thanks for the article.

“Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.”—Archimedes

It also means your hips are moving farther. I think the biomechanics of that motion is more important than just sheer leverage.

i do not feel as comfy or as efficient on 165's...maybe a psychological thing but tis what it tis.
what about femur length.....long tall vs short folks....any data.

Best source of info I have found is the man::

https://www.sheldonbrown.com/cranks.html

Cliff notes version is there are lots of theories and self professed experts, but when you get right down to it who the F knows. Ride what feels right.

Shorter crank arms on a fixed gear bike lessen the risk of pedal strike in corners. Shorter crank arms in general create less knee flexion (a consideration for anyone with knee range of motion issues) and are easier to spin at high rpms. Longer crank arms have more leverage, but I've never been able to feel this with a 5mm difference in length.

Exactly. It's a first class lever,

i have short legs. stand 5'11 but 30 inch inseam so longer arms and torso.
ride 172.5....175 mtb.
thmte are several articles on topic at bottom of the sheldon article..

OP, you are well within the "normal" height range where a 172.5 or 175 will be optimal for your comfort, as you find on your other bikes. But, as explained above by Rolla and JDT, fixed gear pedal strike is why you have the 165 clown crank on your bike. It might be worth it to try a 170 on your fixed gear, especially if you can refrain from leaning much in corners. FWIW, you would need a power meter to determine whether your crank length makes any difference in your output, though people can imagine anything.

not even she cares how long your crank is

It's a psychological thing.

I'm 5'11 with a 32in inseam. I ride 165s after years of 172.5s and 175.

Allows for much more aggressive and aero positions.

Zero power loss, from 1 sec to 5 hours.

Many of us have a crank length that works best for us. I rode 170 my first several bikes including the bike I first raced. Mid-season I changed bikes to one with 175s. First ride was my morning training loop. I went deliberately easy so as not to pull a "surprise" on my knees. That easy ride matched my best time ever. 3 days later, two minutes came off that and continued to fall all summer.

I've stayed with 175s since. They have never not felt "right". Had I never ridden that bike I probably would nave muddled along for years never knowing things could be better.

I had the opportunity to ride a bike with 215mm crankarms. The guy's whole deal was "pedal circle" and he'd ordered a custom frame (Bill Boston?) with a very high bottom bracket to accommodate the cranks. I rode a couple blocks, then turned around and rode back. Massive leverage on the pedals but it felt like my knees were about to smack me in the nose.